Diaphragm pumps include a pump chamber that is divided by a piston or diaphragm so as to provide a first sub-chamber that receives a working fluid (liquid or gas) under pressure, and a second sub-chamber that receives the fluid being pumped. A working fluid under pressure is delivered to the first sub-chamber to cause reciprocation of the piston and diaphragm to vary the volume of the second sub-chamber and thereby pump a fluid therethrough. These diaphragm pumps have an inlet and an outlet that communicate with the second sub-chamber via one-way valves so that the fluid being pumped passes in a predetermined direction through the pump. A first manifold joins the inlet with the second sub-chamber while a second manifold joins the second sub-chamber is with the outlet.
Described in International Patent Application PCT/AU2009000199 (WO 2009/137862 A1) is a diaphragm pump that is operated by air under pressure. The pump includes a valve that provides and coordinates the delivery and exhaust of air with respect to the first sub-chamber. The exhaust air passes through the valve and is delivered to a muffler.
Efficiency of the above described pump is diminished due to resistance of air flow downstream from the valve.